The production of ring members, such as race rings for rolling bearings, especially larger rings, is often effected by forging an annular blank, and then subjecting the blank to cold rolling, followed by other machining operations, such as grinding, honing and the like. During the cold rolling operation, the annular blank, made from a bearing steel of common grade, is rolled and compressed between a mandrel and a forming roll at ambient temperature and in such a manner that the material thickness is reduced. The rolling operation does not result in the removal of any material from the blank and so the diametrical size of the ring increases and, due to the shape of the forming roll, the axial width of the ring is kept substantially unchanged. When using cold rolling, the increase in ring diameter, or the rollability of the material, is often limited to a maximum of about 2 times. In addition, the power consumption is relatively high for driving the forming roll and the receiving roll, which are driven by separate motors. The mandrel is free-wheeling.
Ring production can also be accomplished by hot rolling, with a corresponding machine design and operation, whereby the blank is heated to a material temperature of above 1200° C., at which the rolling operation is performed. The rollability associated with hot rolling is better as compared to the results with cold rolling, but a drawback with this hot rolling method is that the rings produced have a tendency for distortion and warping, and it is necessary to subject the rings for a heat treatment after the rolling operation.
A need thus exists for a method for producing ring members, through use of a rolling operation, in which the rollability is clearly improved in comparison with the cold rolling method, and which also does not suffer drawbacks to the same extent as hot rolling.